Another easy way to set permissions on files and directories is by using your SiteMadeEasy Web Control Panel. Go to http://yourdomain.com/cgi-bin/plusmail and select Site Manager, then click on the icon next to the script you want to set permissions on and follow the prompts.

If, after checking permissions and uploading in ASCII you are still getting "Internal Server Error", try executing the script from telnet and seeing what error messages it produces.